Allow adding multiple properties at once when adding a track to the animation player

[jbauss]

Hi,
I recently started using Godot for a 2D project with sprites that feature a lot of different animations. Currently adding a new animation for a sprite involves the following steps in the Animation tab of the editor for the AnimationPlayer:

1. Click on "Animation" > "New"
2. Click on "Add Track" > "Property Track"
3. Select "Sprite2D" node and click "OK"
4. Select "texture" property and click "Open"

At that point the window closes and a track with the texture property has been added. However I usually want to add multiple properties of the same node as a track to the new animation (texture, hframes, vframes, frame) which means I need to repeat the same process multiple times just to add a new animation.

I suggest allowing the selection of multiple properties in the last dialog like this:

The dialog would allow the selection of multiple properties through:

• CTRL + Click (Keeps the current selection and adds the clicked on property to the selection)
• Shift + Click (Selects all the properties between the last selected property and the clicked on property. If no property has been selected, selects all the properties between the first element in the list and the clicked on property)

This would mimic the behaviour of typical file managers like windows explorer or the file navigators in code editors like VS Code.

Once the user clicks "Open" all the selected properties get added to the animation as separate tracks. One minor nitpick: if possible rename the button "Add" instead of "Open" since we're adding a track.